Benecos Nail Polish - Rock It - 5ml. Benecos Nail Polish Rock It is a medium grey with a hint of mauve giving a warm tone and is perfect for long and short nails. Benecos Nail Polishes are now up to 90% natural and is enriched with nourishing avocado oil and biotin. Biotin is known as Vitamin B7 or Vitamin H (the H is from the German word Haar and Haut meaning hair and skin). Biotin is known for its strengthening effect on brittle nails and helps stop the nail from splitting. Vegan.